It is often desirable to measure properties of a compactible material during the handling, transporting and/or treating of such material. Such measurements are sometimes accomplished by continuously removing a sample of the material from a container or pipe, continuously measuring the properties of the sample and returning the sample to the container or pipe.
Apparatus has been developed for this purpose which includes an auger type conveyor which extends into the material, removes a sampling of the material and conveys the sampling to a measurement station or measuring zone. Often the sampling is subjected to pressure and thus compacted at the measurement station to enhance the measurement process.
Known apparatus of this type, see for example DE-OS 33 29 135, have the drawback of an irregular pressure build-up in the measuring zone. In particular, the material is compacted up jamming the conveyor. In tests attempting to shorten the measuring zone, strong pressure fluctuations occurred and the actually intended pressure value temporarily dropped to zero such that no reliable measuring results could be obtained.
In order to obtain reliable measuring values, stable conditions are required with respect to the material conveyed through the measuring zone. Therefore, substantially isotropic conditions must be established in the measuring zone, particularly in the sensing range of the parameters to be determined.